Donald Trump 'mixes up' cities in tweet about latest mass shooting

US President Donald Trump has come under fire for appearing to offer his condolences to the victims of the wrong US shooting.

Four people were slain after a gunman stormed Rancho Tehama Elementary School in California today.

Trump took to Twitter this afternoon (AEST), but he tweeted about the "people of Sutherland Springs, Texas".

Last week, Sutherland Springs was left reeling when David Patrick Kelley entered the First Baptist Church and opened fire on the congregation, killing 26 people.

In the hours after today's US shooting, Mr Trump offered the words: “May God be with the people of Sutherland Springs, Texas. The FBI and Law Enforcement has arrived”.

Social media users have been quick to criticise the former billionaire real estate mogul for his glaring error, with high-profile British journalist Piers Morgan one of the first to unleash a biting response.

“At least get your mass shootings right, Mr President. This was last week. The new one is in California,” Morgan wrote.